1. Field of the Invention
The present invention relates generally to the fields of pharmaceutics and drug delivery. More particularly, it concerns alkyl substituted polylactides which may be used to deliver a drug without the need for an organic solvent.
2. Description of Related Art
Biocompatible and biodegradable polylactides/glycolides (PLA/PLGA) have received high attention over the last thirty years in the biomedical field as sutures, implants, colloidal drug delivery systems (Penning et al., 1993; Uhrich et al., 1999), and more recently also in tissue repairing and engineering (Liu and Ma, 2004; Stock and Mayer, 2001) and anti-cancer drug delivery (Mu and Feng, 2003; Jiang et al., 2005). Next to the medical field they are also widely used in the packaging area. As biodegradable “green polymers” they are preferable to the commodity polymers currently used (Drumright et al., 2000; Vink et al., 2003).
There is a crucial need of well-defined polylactide-based materials with advanced properties to fit all the requirements for the different applications. For example, PLA/PLGA homo- and co-polymers synthesized by the well-established ring opening polymerization (ROP) process (Dechy-Cabaret et al., 2004; Kricheldorf et al., 1995; Schwach et al., 1997; Degee et al., 1999; Ryner et al., 2001) have a glass transition temperature (Tg) limited to a range of only 40-60° C. (Jamshidi et al., 1988; Vert et al., 1984), independent of the polymer molecular weight and chemical composition. This combined with interesting mechanical properties makes them suitable in medical applications as biodegradable implants, bone fracture fixation devices, scaffolds for living cells.
These polylactides, however, have significant limitations for drug delivery purposes. For drug delivery purposes, polylactides need to be formulated with organic solvents and administered as solutions or in form of nano- and micro-particles, and polylactides can not be injected on their own. Thus there is a significant need for a polylactide which may be used for drug delivery that does not require the use of an organic solvent or to form nano- and micro-particles.